This invention relates to a food, and more particularly to a semi-moist pet food.
Within the class of foods known as pet foods, there are three basic subdivisions--dry pet food, semi-moist pet food, and moist pet food.
In general, the dry pet food--due to its low moisture content which is usually less than about 15 percent--tends to exhibit the greatest microbiological stability and requires no special handling or package upon distribution.
At the opposite end of the spectrum is the moist pet food having a moisture content in excess of about 50 percent. Due to the high moisture content of the moist pet food, microbiological stability is a major problem. This problem in a moist pet food is overcome only by heat sterilizing the moist pet food, and by packaging the moist pet food in a hermetically sealed container. Even with heat sterilization and hermetically sealed packaging, refrigeration is required after the package of moist pet food is opened to preserve the leftover pet food for even a short time.
Semi-moist pet food has a moisture content generally ranging from about 15 to 50 percent. Since semi-moist pet foods are higher in moisture content than dry and lower in moisture than canned, special technology is required to render it microbiologically stable. This moisture content in combination with such special technology may product a microbiologically stable pet food which does not require refrigeration. At the same time, the higher moisture content of the semi-moist pet food provides an increased palatability when compared to the dry pet food.
A semi-moist food must contain a microbiological inhibitor system which will stabilize it again microbiological degradation. While almost any microbiological inhibitor system is suitable for use in the semi-moist food of this invention in an amount sufficient to provide microbiological stability, there are three systems that are especially operable for the purpose of this invention. A first system for microbiological stability may be defined as a low sugar, high polyhydric alcohol content microbiological stability system. This first system is exemplified by Canadian Patent No. 1,020,399 to Burkwall incorporated herein by reference. A second system for microbiological stability is a high acid and low polyhydric alcohol content system. This second system is exemplified in U.S. Pat. No. 4,011,345 to Bartsch incorporated herein by reference. A third system for microbiological stability is a high sugar or high water soluble solute content system. This third system is exemplified by U.S. Pat. No. 3,202,514 to Burgess, incorporated herein by reference. These systems may be used singly or in combination and with other systems so long as microbiological stability is achieved.
If the first system is used the microbiological stabilizer system for the semi-moist pet food of this invention comprises at least one polyhydric alcohol. A typical polyhydric alcohol component suitable fur use in this invention is disclosed in the Canadian Patent to Burkwall above-referenced. Preferable polyhydric alcoholds are propylene glycol and 1,3-butanediol used individually or in combination. From about 2 to 20 percent of the polyhydric alcohol alone or in combination with sugar is used to stabilize the product by preventing microbiological growth. While the sugar as above defined also contributes to the stability of the pet food by lowering the water activity, sugar is not required.
If the second system is used, a means of achieving semi-moist stability is to adjust the pH of the food product to 4-6 and use 3-9 percent polyhydric alcohol. No sugar is used or required but small amounts may be optional for flavor, or palatability. Typical foodgrade acids for use to adjust the pH in the semi-moist food include acetic acid, lactic acid, adipic acid, succinic acid, and inorganic acid such as phosphoric acid, sulfuric acid, hydrochloric acid, or mixtures theref. Furthermore, the foodgrade acid salts, which may be used to adjust the pH of the food, include monocalcium phosphate, monosodium phosphate, aluminum sulfate, aluminum ammonium sulfate, aluminum calcium sulfate, aluminum potassium sulfate, aluminum sodium sulfate, and mixtures thereof.
If the third system is used, large amounts of sugar or water soluble solutes such as polyhydric alcohols are used to substantially reduce the water activity and stabilize the food from a microbiological standpoint. Typical sugars used are sucrose and corn syrup. By "sugar" is meant any edible sugar used in the food art. Substantial examples of suitable sugars for use in the food art are listed in U.S. Pat. No. 3,302,514 to Burgess, et al. incorporated herein by reference. A suitable amount of sugar or water soluble solutes for use in this product ranges from about 15 percent by weight to about 35 percent by weight of the final product.
An antimycotic may be added to all three of the above microbial inhibitor systems in an amount sufficient to aid in preventing mold growth. The antimycotic is generally an edible antimicrobial acid or acid salt. The antimycotic is present in the food in an amount of 0 to 1 percent by weight of the pet food. More preferably, the antimycotic is present in an amount of 0.01 to 0.9 percent by weight. Typical edible acids and their salts suitable for antimycotic use include benzoic acid, the benzoate salts, the paraben salts, propionic acid, and the propionate salts, acetic acid and the acetate salts, sorbic acid and the sorbate salts and mixtures thereof. Especially preferred antimycotics are potassium sorbate and sorbic acid.
Various other common additives from 0 to about 25 percent may also be added to the food whether it is a semi-moist food or not. Fat is usually added in an amount from 0 to about 12 percent by weight of the final product depending on how much fat is naturally contained in the meat or meat by-products used. The fat may be of either animal or vegetable origin. A preferred fat for use in a pet food is an animal fat exemplified by prime steam lard, tallow, and choice white grease, although fish and chicken fat, cotton seed, corn oil, soy oil, peanut oil, sunflower oil and other vegetable oils can be used.
For flavor and nutritional purposes common additives include a variety of salts to be added to this pet food. Typical salts suitable for use in this invention include iodized salt, regular salt, potassium chloride, and other suitable edible salts. Vitamins, supplements, mineral supplements, colorings, flavorants and antioxidants are generally present in the pet food in a sufficient amount (generally about 0 to about 5 percent) to provide nutrition and to add to overall appearance. Included in the vitamin and mineral supplements ae ingredients such as choline chloride, magnesium oxide, vitamin A, B.sub.12, D.sub.3, and E, riboflavin, niacin, folic acid, pyridoxine hydrochloride, thiamine mononitrate, calcium pantothenate and other suitable vitamins and minerals.
Generally speaking, within the moisture range of food products which are characterized as semi-moist, the higher moisture-containing products are found to be more palatable.
Nonetheless because of processing problems the upper limit of moisture contents for many highly advantageous combinations of ingredients has been believed to be about 30 percent. (See Burgess U.S. Pat. No. 3,202,514.) For example, above 30 percent moisture level pet foods containing combinations of oil seed protein sources and meat based protein blends and amylaceous based nutrients are found to exhibit stickiness before and after extrusion, and during storage, which renders the formulation using such combinations substantially unusable in commercial production operations.
Admixed semi-moist pet food ingredients are conventionally conveyed to a cooker-extruder using screw-type conveyor-feeders. The use of an ingredient formulation which exhibits substantial stickiness causes considerable problems with respect to erratic flow of the ingredients through the pre-cooker-extruder conveying system. Also, the extruded semi-moist pet food is conventionally cut at the point of extrusion or shortly thereafter using a multiplicity of rotating knives, dicers, or other conventional cutting equipment. With respect to the use of high speed rotating knives, the semi-moist product is necessarily thrown at high speed and often hits against the walls of safety shields surrounding the high speed cutting systems, and is ultimately thrown onto a conveyor positioned substantially below the point of extrusion and cutting. Contact of a sticky product with the walls of the shield can cause the product to adhere to the wall of the shield. Subsequent contact with the following recently cut material leads to cohesion and possibly obstructive build-up of material within the knife shield system. Also, the discrete particles falling on the conveyor, should desirably remain as discrete particles but it is most likely that, with a sticky product, the discrete particles will cohere to one another on the conveyor forming irregular masses of shapes.
Likewise the semi-moist pet foods are conventionally processed at high speeds through apportioning and packaging equipment in which it is absolutely essential that discrete particles of the product be readily separated into the desired portions at high speeds. Whenever a formulation results in a sticky product such high speed apportioning and packaging is rendered virtually impossible. The economy of products made available to the ultimate consumers depends, to a great measure, on the output rate of the commercial manufacturing and packaging equipment.
Semi-moist pet foods having moisture levels in the range 31-50 percent inclusive containing blends of oil seed protein source ingredients with meat protein source ingredients, and amylaceous ingredients, upon mixing as well as upon extrusion are usually so sticky and cohesive that the extrusion of discrete particles results in clumping and cohesion to such an extent that the problems discussed above are encountered and the normally used packaging and handling equipment are rendered useless.